9:37 PM [Daniel]. I may take back some of my earlier remarks about Sestak. If he is actually winning Delaware county, then Specter probably does have serious problems. The real problem with drawing conclusions at this point is that most of the results we have so far are not representative in the Philly suburbs, so we are seeing massive swings between each set of precincts. That said, the shrinking Specter margin in Philly, and the low turnout there looks to be a problem for the incumbent.

This is what gives me pause before pointing people to look at Tim Holden, who seems to be having something of a challenge in his primary, and Mary Beth Buchanan, the former US Attorney and NRCC recruit for PA 4, who seems to be losing badly. Tom Marino, another former US Attorney is having trouble in the 10th, though he is now leading by about 4 points.

9:36 PM [Nate]. In KY, keep in mind that there are still a few Lexington and Louisville precincts to report. Those are a bit of an insurance policy for Conway.

9:32 PM [Nate]. Sestak and Specter are basically tied and Philly is OVER-represented so far; this bodes well for Sestak.

9:28 PM [Nate]. We’ll be transitioning to a new thread in a few moments here. I have to leave for a TV hit (MSNBC) shortly so Ed will be captaining the ship for a bit.

9:26 PM [Nate]. Daniel, I somewhat disagree on Pittsburgh. Specter got the mayor’s endorsement there, and it’s a big union town. If Sestak’s winning by only 4 percent there, seems about par for the course.

9:23 PM [Nate]. Our completely unsophisticated model still thinks Conway is more likely than not to hold on. Swing State Project’s slightly-less-unsophisticated one thinks so also.

9:15 PM [Ed]. All those early Arky returns are from the 4th CD in southern Arkansas (plus Yell County just outside it). This is not Morrison’s home area; he’s from Jonesboro up in northeast Arkansas. We’ll have to see if he’s doing anything like this well in more populous counties, but I agree, it looks like big trouble for Lincoln.

9:13 PM [Ed]. Back in KY, Mongiardo has pulled to within 13,000 votes of Conway, and is really doing well in WKy. Looks like he’ll have a plurality of nearly 1500 votes in Graves County just south of Paducah.

9:13 PM [Daniel]. I think Sestak is in serious trouble. He is only winning Pittsburgh by 4% which is nowhere near enough to counteract being destroyed elseware, especially in Philly. And as proof Philly is not his problem, Onorato has easily pulled ahead despite losing there.

9:09 PM [Nate]. Mongiardo needs to win by about a ~17% margin among the remaining precincts to make up his deficit to Conway.

8:53 PM [Daniel Berman]. I think you are seeing evidence of this in the unknown candidates who are winning 13% in the Democratic primary. Despite most of them being to the left, i suspect they are none-of-the-above votes, and I would not be shocked if a lot of them do not vote Democratic in November. Watch Morrison’s voters for the same thing in Arkansas.

8:50 PM [Thomas Dollar]. Dan, that registration gap is interesting. KY, of course, is a conservative state that votes Republican in national elections. If many of those conservative voters are “legacy” registered Dems, then you have a much more insular Republican primary pool, and one that’s more amenable to an unorthodox candidate like Rand Paul. I wonder what would have happened in an open primary, or if those conservative voters were voting in the Paul-Grayson race.

8:48 PM [Ed]. With just over half the precincts reporting from McCracken County (Paducah), Mongiardo’s winning 57-32, and should take a plurality of over 1,000 votes out of that county.

8:46 PM [Nate]. In very early returns in Arkansas, Morrison has 18% of the vote. If he’s that high, a runoff is very likely.

8:44 PM [Dan Berman]. Just an interesting point, the 60% or so by which Democratic turnout is exceeding Republican turnout in Kentucky is almost exactly the margin by which Democratic registration exceeds Republican registration(1.6 million to a bit over 1 million).

8:43 PM [Thomas Dollar]. I’ve never thought the Tea Party was anything more a new name for various factions of disgruntled conservatives. With Rand Paul’s big win, the Tea Party may get redefined as being Paulites. Gold standard, abolish the Fed, pre-(Teddy) Roosevelt era Federal government–stuff that should make the Rick Santellis of the world a bit nervous. How does Mitch McConnell spin this one?

8:42 PM [Nate]. Specter has jumped out to an early lead, but almost all of that vote is from Philadelphia.

8:37 PM [Nate]. Although there’s very little Louisville/Lexington vote left, Mongiardo is going to have to pick up the pace a bit in rural counties if he wants to overtake Conway. Right now, our crude extrap-o-jection shows Conway winning 47.1 to 43.3.

8:35 PM [Ed]. From scattered early returns, it’s appears that every mile you go west of Bowling Green takes you further into Mongiardo Country. But it’s unclear whether the Dr.’s margins there will be enough to overcome Conway’s urban onslaught.

8:30 PM [Nate]. Polls closed in Arkansas.

8:11 PM [Nate]. Democratic turnout is about 60 percent higher so far.

8:09 PM [Ed]: Very early returns from WKY:

Warren County (Bowling Green): Conway up 53-35.Graves County (Mayfield): Mongiardo up 54-36.

7:56 PM [Nate]. Our super-simple extrapolation now shows Conway projected to win 45.9-41.9. Margin of error is definitely too large to come to any conclusions.

7:55 PM [Ed]. Still nothing in from Western KY, which was supposedly a real battleground.

7:54 PM [Nate]. AP calls it for Paul (about 1/2 hour after we did.)

7:48 PM [Nate]. Conway’s numbers are holding up better in other rural areas than they were in the Eastern portion of the state. The crude projection method I describe a moment ago now shows him winning 44.8%-42.7%.

7:47 PM [Ed]. Well over half the precincts in Jefferson County (Louisville) are now in, and Conway’s leading 60-27, while Paul’s leading 60-37.

7:43 PM [Nate]. By the same method, I get Paul winning 56-38.

7:38 PM [Nate]. Based on a crude extrapolation of the vote in from Fayette County (Lexington), Jefferson County (Louisville), and “rest of state” so far, I show final results of Mongiardo 214,701 (43.7%), Conway 214,075 (43.6%). It might be very close!

7:06 PM [Daniel Berman]. You know, for all the hits Kentucky gets for being backwards, Trey Greyson has one hell of a good SOS site. Makes me feel a bit bad about what looks to be happening tonight.

Anyway, early numbers look good for Conway. He is winning Lexington comfortably and Dr. Dan is not cleaning up in Appalachia.

7:01 PM [Ed]. The majority of the raw vote listed on the SoS site is from Fayette County, where Paul’s up 62-34 and Conway’s up 52-36.

6:57 PM [Nate]. Although it’s early, this looks very safe for Paul if he’s leading by 12 points in the Eastern portion of the state.

6:48 PM [Ed]. Still too few counties from the 5th reporting to reach any real conclusions; about half the reporting counties are from central KY.

6:45 PM [Nate]. So far, Democratic turnout is a notch (35 percent) higher in Kentucky. But D’s have a big registration edge in Kentucky and it has closed primaries, so not hugely surprising.

6:39 PM [Nate]. Just a trickle of results in from Fayette County — Lexington — so far. Conway leads the Donkeys there 52-36, Paul leads the Elephants 60-37.

6:37 PM [Ed]. I’d say the thing to look for early is whether Paul is winning in Eastern KY’s 5th CD, which was the only CD where Grayson was winning in the final Magellen poll. That’s Hal Rogers’ district (he strongly supported Grayson), and a mountain GOP area that’s relative moderate on economic issues, thanks to TVA.

This CD is also Mongiardo’s base.

If Paul’s winning in the 5th, it could be a statewide blowout.

If Mongiardo’s losing the 5th, he’s in deep trouble.

6:32 PM [Nate]. To the extent there are any results in from Kentucky so far, they’re from the Southeastern portion of the state which is supposed to be comparatively more favorable for Mongiardo and Grayson.

6:07 PM [Nate]. The Democratic primary in Kentucky has been strangely ignored; we have Conway doing a couple of points better against Paul than Mongiardo, so it’s not without consequence.

6:04 PM [Nate]. Bear in mind that there aren’t likely to be any exit polls tonight, so there won’t likely be any early “calls” of races.

5:58 PM [Nate]. I saw Blumenthal’s prepared remarks today but haven’t seen the Q&A. Bottom line: it was the sort of event that will play well to those who were sympathetic toward him in the first place, but won’t erase doubts among those who weren’t. The Democrats would be committing malpractice not to be polling the living daylights out of Connecticut and seeing what impact the scandal has had.

5:50 PM [Nate]. Polls close in most of Kentucky in about 10 minutes. We’ll be here all night to cover the Bluegrass State and rest of the races; you may also want to follow our twitter feed.

Nate Silver is the founder and editor in chief of FiveThirtyEight. @natesilver538